The disability may be connected to special needs at the time of the adoption. I am not sure what was in place when she was adopted but if she had been born addicted and had any other issues present early on she might have qualified for SS adoption assistance.
I found this about financial assistance. I bolded the exception that might have given them an SSI subsidy for the children. I bolded the factor that would have applied b/c t is based on sibling group in No. 1. I also added No. 6 from the page. It is from:
http://www.nacac.org/adoptionsubsidy/stateprofiles/pennsylvania.html
WHO IS ELIGIBLE FOR ADOPTION ASSISTANCE?
1. How does Pennsylvania define special needs to determine eligibility?
A child with special needs is defined as a child who meets all three of the following criteria:
The child is free for adoption.
The child has a qualifying factor or condition (see list below).
Reasonable efforts were made to place the child without adoption assistance unless it is not in the child’s best interest; for example, if there is the existence of significant emotional bond between the adoptee and the adoptive parents
For a child to be determined to have a qualifying factor or condition, he or she must meet at least one of the following circumstances:
Be five years of age or older and under the age of 18 or 21
Be a member of a racial or ethnic minority group
Be a member of sibling group of two or more placed together in the same adoptive home BBM
Have a physical, mental, emotional condition or disability
Have a genetic condition that indicates a high risk of developing a disease or disability
6. When do adoption assistance payments begin?
Adoption assistance payments and benefits begin on the effective date of the agreement. That date may be before adoption finalization when all four of the following criteria are met:
• Parental rights to the child under 18 years of age have been terminated.
• Child is placed in the prospective adoptive home.
• The adoption agreement has been signed.
• The adoption petition has been filed.